Various methods for achieving three-dimensional stereoscopic display in a video display device have been studied. A method of preparing right-eye video and left-eye video of a subject, providing a mechanism of making the right eye and the left eye see them, respectively, and performing stereoscopic vision of the subject is well known. When a person sees something with the eyes, generally, parallax occurs between the image seen by the right eye and the image seen by the left eye even if the person sees the same subject. This parallax allows the person to stereoscopically recognize the seen subject and feel the depth of the subject. Therefore, by preparing a right-eye video signal and a left-eye video signal having the parallax, a video display device capable of stereoscopically viewing the subject is achieved.
Next, the parallax between the right-eye video and the left-eye video is described. For example, as the subject in the right-eye video is shifted to the left side and the subject in the left-eye video is shifted to the right side, a person seeing the videos feels as if the subject projects to the front side. Conversely, as the subject in the right-eye video is shifted to the right side and the subject in the left-eye video is shifted to the left side, a person seeing the videos feels as if the subject is recessed to the depth side. When there is no parallax and the right-eye video is the same as the left-eye video, it looks as if the subject exists at a position of the display surface of the video display device. The videos having such parallax allowing stereoscopic vision can be easily acquired by photographing the subject with two same cameras arranged horizontally in parallel. At this time, generally, a right-eye camera is disposed on the right side and a left-eye camera is disposed on the left side.
Various systems have been proposed as a video display device for three-dimensional stereoscopic vision. For example, in an active shutter system, the right-eye video and the left-eye video are sequentially arranged and displayed in time sequence. When shutter eyeglasses are used where the right-eye lens and the left-eye lens are opened or closed in response to the right-eye video and the left-eye video, respectively, the right-eye video is seen only by the right eye and the left-eye video is seen only by the left eye. This allows stereoscopic vision of the subject (patent literature 1).
When a video signal for stereoscopically viewing a subject is transmitted, a right-eye video signal and a left-eye video signal need to be transmitted individually. Therefore, when the right-eye video signal and left-eye video signal are transmitted as they are, the transmission rate is twice that in a usual case.
For example, in a field sequential system shown in FIG. 7A, left-eye video L and right-eye video R are arranged in time sequence for each frame and are transmitted. In this system, a signal where neither vertical resolution nor horizontal resolution does not degrade is acquired when stereoscopic vision is not performed, namely when two-dimensional display is performed. However, the transmission rate is twice that in the usual case.
For suppressing the transmission rate, several types of systems shown in FIG. 7B, FIG. 7C, and FIG. 7D are disclosed. In a side-by-side system shown in FIG. 7B, right-eye video R and left-eye video L with a horizontal resolution of ½ are transmitted while being arranged in a right half and a left half of one frame. In this system, however, the horizontal resolution degrades. In a vertical interleave system shown in FIG. 7C, left-eye videos L and right-eye videos R are vertically transmitted in a multiple manner for each line. In this system, however, the vertical resolution degrades. In a checker pattern system shown in FIG. 7D, right-eye videos R and left-eye videos L are transmitted while being arranged in a zigzag pattern for each pixel. In this system, however, both the vertical resolution and horizontal resolution degrade.
Video signals to be transmitted in such systems are encoding-processed by an MPEG2 encoding system or MPEG4-AVC/H.264 encoding system used for recent digital broadcasting, and then transmitted or recorded in an accumulation medium. Thanks to the encoding processing, the transmitting efficiency can be improved by compressing data amount. However, the encoding processing generates an encoding noise accompanying the compression processing, and also causes image quality reduction. The encoding noise includes a block noise that is generated in a boundary between blocks by performing a series of encoding processings block by block, and a ringing noise (also called mosquito noise) that is generated by quantization processing. Conventionally, a method of detecting these encoding noises and reducing the noises by filtering processing is proposed (patent literature 2).
In such a method, a noise is extracted from a video signal with a high pass filter (hereinafter referred to as “HPF”) and a band path filter (hereinafter referred to as “BPF”). However, actually, the noise is often difficult to be distinguished from a picture in the video signal and false detection is often caused, so that a side effect that the picture is blurred by filtering processing is produced. The noise reducing effect is difficult to be produced dependently on the characteristic of the filter, disadvantageously.
In the conventional art, in reducing the encoding noise such as a block noise or ringing noise that occurs when the video signal of three-dimensional stereoscopic display is encoding-processed by the MPEG2 and H.264, the noise is actually difficult to be distinguished from the picture in the video and false detection often occurs. As a result, the filtering processing for noise reduction blurs the picture or the noise reducing effect is difficult to be produced dependently on the characteristic of the filter, disadvantageously.